Slit apex seals



Dec- 10, 1963 HANNs-DIETER PAscHKE 3,113,526

sLIT APEX SEALs Filed April 11, 1962 INVENTOR. HANNEx-DIETER FAEEHKEATTFINEY United States Patent O The present invention relates broadly tothe art of rotary mechanisms and is particularly directed to sealingmeans for such rotary mechanisms.

The invention is particularly useful in connection with rotarymechanisms similar to that disclosed in US. Patent No. 2,988,065,although as will become apparent, this invention is not liniited to thisspecic type of rotary mechanism. In the following description theinvention is described in relation to an internal combustion engine butthe invention is also suitable for fluid purnps and uid motors.

A rotary engine as disclosed in said patent comprises an outer bodyhaving a cavity therein and an inner body or rotor disposed thereinrotatable relative to the outer body, about an axis laterally spacedfrom but parallel to the axis of said cavity. The inner body isjournaled on an eccentric portion of a shaft which is co-axial with theouter body and journaled in bearings carried by the outer body endwalls. The outer body or housing has axially-spaced end walls and aperipheral wall interconnecting the end walls to form said cavit theinner surface of the cavity peripheral wall having a multi-lobed profilewhich preferably is basically an epitrochoid. The inner body or rotorhas end faces disposed adjacent to said outer body end walls for sealingcooperation therewith and has a peripheral surface with a plurality ofcircumferentially-spaced apex portions, each carrying a radially-movableseal for sealing engagement with the multi-lobed inner surface of theouter body peripheral wall to form a plurality of working chambersbetween the two bodies which vary in volume upon relative rotation ofthe two bodies. Each apex seal of the inner body runs axially from oneend face to the other of the inner body.

Prior combustion engines of this type have had a groove at each apexportion of the inner body in which single radially-movable seal stripwas disposed, said seal strip separating the adjacent working chambers.The full depth of the apex strip, as measured radially, is composed of apartial depth received in its groove, plus the remaining strip depthexposed to the combustion gases in the working chambers, this exposedportion extending between the inner-body apex-portion surface and theinner surface of the outer body. During operation of the engine the apexseal strips may be subjected to uneven heating because theradially-inward part of the apex seal strip which is situated in thegroove in the rotor apex portion is able to dissipate a part of its heatthrough the groove wall to the rotor, whereas the radially-outward partf the apex seal strip that projects beyond the rotor has no directcontact with either the inner or outer body except along its outer edgeand therefore said projecting portion of the apex seal strip becomeshotter than the remainder of the apex seal strip. As a result, the edgeportion of the apex seal strip projecting from the rotor acquires anoutwar ly convex shape to produce gaps between the end portions of thestrip and the outer-body peripheral wall thereby impairing the sealingengagement of the strip with the outer body peripheral wall and causingleakage of gases between the Working chambers.

In addition, such a convex seal strip may rock about its point ofcontact with the peripheral wall as the en- Mice gine operates. Any suchrocking movement can lead to injury to the peripheral-wall innersurface.

An object of the present invention comprises the provision of a rotarycombustion engine in which a novel apex seal arrangement for the Workingchambers is provided to maintain continuous and improved sealing duringengine operation.

Speciiically, instead of providing only a single seal element at eachapex portion, acting as a partition between the two adjacent Workingchambers, this invention provides at least two seal strips in each apexgroove, and extending over the entire width of the rotor, with at leastone or" the seal strips in each apex groove having a plurality of slitsthat extend inwardly from its radially-outward edge and with the otherseal strip covering said slits. Preferably each apex seal strip hasslits extending inwar ly from its outer edge and also has slitsextending outwardly from its inner edge. Such a slit apex seal stripwill more nearly contact the inner surface of the outer bodynotwithstanding non-uniform temperatures of said seal strip ordeformation of said inner surface.

Such a slit apex seal strip has the further advantage in that the slitsprovide the seal strip with a substantial flexibility in itslongitudinal direction. As a result of this flexibility each apex sealstrip can be made to sealingly engage the outer body end walls withoutdanger of becoming clamped therebetween because of expansion of saidseal strips relative to the outer body. Accordingly, a further object ofthe present invention resides in the provision of novel apex sealconstructions in which the apex seal strips have longitudinalilexibility to insure sealing at the ends of these seals.

A further object of the invention resides in a novel construction of theapex seal strips for reducing the manufacturing costs. ln accordancewith the invention, the slits are non-symmetrically spaced in anidentical manner along each seal strip. With this seal construction,each pair of seal strips in a groove can be oppositely disposed so thateach strip covers the slits in the adjacent strip notwithstanding thefact that the seal strips are slit in an identical manner.

Other objects of the invention will becorne apparent upon reading theannexed detail description in connection with the drawings in which:

FIG. l is a partial, longitudinal, sectional view through a rotor apexportion and groove showing a prior art form of unslit apex seal strip;

FIG. 2 is a View similar to FIG. l, except showing the slit apex sealstrip in accordance with the invention, and as taken along line Z-Z ofFlG. 3;

FG. 3 is a partial View of the rotor apex portion and a pair of slitseal strips as taken along line 3*-3 of FIG. 2;

FlG. 4 is an enlarged, front-elevation view of a pair of slit apex sealsin accordance with the invention;

FIG. 5 is a top View of a pair of slit apex seals as taken along line 55 of FIG. 4;

FIG. 6 is an enlarged, partial, front-elevation View of a pair of slitapex seals.

Referring to the drawings, as illustrated in FIG. 1, the housing of arotary combustion engine comprises spaced end walls ll and l2, and aperipheral Wall 13 disposed between and interconnecting said end walls.The inner surface lll of the peripheral wall ll3 preferably has amulti-lobed profile in cross-section which is basically an epitrochoid.Inside and eccentric to the housing is disposed an inner body or rotorl5, having preferably spaced apex portions le at each of which is anoutwardly-facing apex groove 17 recei ing a radially-movable seal stripitl for separating adjacent working chambers lll. The prior art form ofunslit seal strip i8 is urged outwardly in sealing cooperation with theinner surface lltof the peripheral wall 13, partly by spring means 2l)and also by gas pressure coming into the groove 17 from an adjacentworking chamber 19. Each end of the apex seal strip 18 is in sealingcooperation with an intermediate sealing element 21, which is alsoreceived within the apex groove 17 at its ends. This intermediatesealing element 21 is axially movable 'and is in sealing cooperationwith the adjacent surface o' the outer-body end wall l1 or l2. Betweenthe intermediate sealing elements 2l, disposed on each end face of therotor 15 and associated with a working chamber 19, are end-face-sealingstrips 22. All of these seal elements and strips act to seal the workingchambers 19.

In the prior art form of radially-movable, unslit, apex seal strip 18 asillustrated in FIG. l, particular difficulties may arise when the mediumin the working chamber 19 has a high temperature, as in the case of arotary combustion engine. The temperature of the unslit seal strip lbecomes unevenly distributed across the seal strip because theradially-inward or inner edge 23 of the strip i3, which is received inits apex groove 17, loses heat to the rotor l5 mostly by conduction andacquires a lower temperature than the radially-outward or exposed outeredge 24 of the strip l8r. The temperature difference between the part ofthe outer edge 24 and the part at the inner edge 23 of the strip 18 canamount to 150 C. to 200 C. in the case of apex seal strips in certainrotary combustion engines.

Because of the temperature difference between the edges 23 and 24, theapex seal strip 18 becomes deformed, assuming a new shape, with theouter edge 24 l'acquiring an outwardly-curved convex profile. As aresult of this thermal distortion, the strip lt! bears against the innersurface of the peripheral Wall 14 only at the middle portion of thestrip i8, as illustrated in FIG. l, during engine operation, and gaps 25me formed on both sides of the middle portion, which impairs thesealing. The magnitude of the gaps l5 has been greatly exaggerated inthe drawing for purpose of illustration.

In addition, because of said thermal distortion, each end face 26 of theapex seal strip i8 becomes slanted relative to the surface of theouter-body end wall l1 and 12, as illustrated in FlG. l, so that theouter corners of the strip, which are located at the intersection of theouter edge 24- and the end face 25, dlg into the outerbody end walls lland l2. As a result, the radial movement of the strip i8 may becomerestricted and its sealing cooperation with tie inner surface of theperipheral Wall 14 and with the end wall lll and l2 also may becomeimpaired.

Another diiiiculty with the prior art form of unslit apex seal strip i8also results from outwardly-curved convex profile of the strip 1S asmentioned above and the limited contact only at the middle portion ofthe outer edge 24 of the strip l. This added difculty is that the apexseal strip 18 may rock about its point of Contact with the peripheralwall 133 as the engine operates. Any such rocking movement can lead toinjury to the inner surface of the peripheral wall 14 of the outer body.

As shown in FlGS. 2 and 3, in accordance with the invention, tworadially-movable, slit, apex seal strips 27 :and 28 are disposedside-by-side in each rotor apex groove 17 in place of the prior art formof the single :strip 1S as shown in FIG. l.

Each such apex seal strip 27 and 2d has a plurality of spaced slits 29and 3i) respectively which extend inered by the adjacent seal strip 27.

Such a slit apex seal strip 27 and 22 will because of r4 its flexibilitymore nearly contact the inner surface of the outer body ldnotwithstanding non-uniform temperatures oi said seal strip 27 and 23 ordeformation of said inner surface i4. A

The radially outward edge 24 of each slit apex seal strip will stillbecome deformed slightly due to the nonuniform temperatures, but insteadof the outer edge 24 assuming an outwardly-curved convex profile overthe strip length as in the case of the prior art form of unslit strip18, as illustrated in FlG. l, the outer edge 24 of each slit strip 27and 28 will assume a prolile of a plurality of small, outwardly-curvedarcs between the slits as illustrated in FIG. 6. Each small are is muchsmaller in height and the total arc is of much less outward curvaturethan that of the above mentioned convex proiile of the unslit strip 18;with the result that the outer edge 24 over the length of the slitstrips 27 and 28 will more nearly Contact the inner surface 14 of theouter body. Also, since the strip 27 and 28 are slit, the corners do notbecome slanted and thus do not dig into the end walls l1 and 12.

Accordingly, as illustrated in FIGS. 2 and 6, the outer edge 24 of theslit strips 27 and 223 will bear against the inner surface i4substantially along the entire length of the strip and not just at themiddle portion of the strips. As a result there are no substantialsealing gaps between the strips 27 and 2S and the outer body, and inaddition the aforementioned rocking movement of said prior art unslitseal strips is avoided.

Furthermore, the plurality of slits 29 and 3i) give the apex seal strips27 and 23 a substantial longitudinal ilexibility compared to that of theusual unslit strip, which insures sealing engagement of its end faces 26with the end walls l1 and l2, provides for control of the frictionalcontact with said end walls, and avoids clamping of the strips 27 and 23by the end walls ll and l2.

Due to the elasticity of the strips 27 and 28 the friction between theend faces 2e and the end walls l1 and l2 can substantially be determinedso that this friction restraint on the radial movement of the apex sealstrip is known and the apex seal strip spring 2d can be desinned toinsure radially outward movement of the seal strips against the innersurface i4.

Also, due to the greater elasticity of the slit strips 27 and 2S, theycan better adapt to the deformations of the inner surface of theperipheral wall 1.4.

To increase the longitudinal flexibility of each seal strip 27 and 28,each of these strips has a slit adjacent to at least one of its ends.Thus, one of the slits 29, designated 2%, in the strip 27 is disposedadjacent to one end of the strip, and similarly one of the slits 30,designated 39a, in the strip 23 is disposed near one end of this strip.The slits 29a and Stk run parallel to the adjacent edges 26 of theirrespective strips 27 and 28. in this way, a sort of yieldable lip 33 isformed at one end of each seal strip 27 and 2E by their respective slits29a and 39a. The gas pressure which enters the slits 22a and 33a forcesthe adjacent lip 33 into sealing engagement with the adjacent outer-bodyend Walls 1l and l2.

For the purpose of increasing the elasticity of the apex seal strips 27and 28, there are preferably also provided in addition to the outer edgeslits, a plurality of spaced slits 3l and 32 extending outwardly partway from their inner edge 23 with said, latter, inner-edge slits beingcovered by the wall of the apex groove i7. The increased elasticity ofthe slit strips 27 and 28 improves sealing of their end faces 26 withthe end walls l1 and l2- and of their outer edge with theperipheral-wall inner surface 14.

ln order to simplify manufacture, it is possible to make all the slitapex seal strips 27 and 2S with outer-edge slits 29, 29a, Si) and 30a asidentical parts. In each apex groove 17, there is a pair of slit sealstrips 27 and 2S with the strips of each pair having outer-edgeradiallyinward slits 29, 29a, 30 and 30a of identical non-symmetricalspacing, but with said pair of strips 27 and 28 being oppositelydisposed in the groove 17, so that each strip 27 and 28 covers theouter-edge radially-inward slits 29, 29a, 30 and 30a in the other ofsaid pair. That is, the slits of the rst strip 27 are covered by theother adjacent strip 28 because, during assembly of the strips in theirgroove 17, the other strip 28 is turned one hundred eighty degrees (180)about its middle before being placed in the groove adjacent to the rststrip 27.

Both of the above seal strips 27 and 28 in each groove 17 are slit. Itis also possible to provide an unslit seal strip in the groove to coverthe slits of the adjacent slit seal strip.

While I have described my invention in detail in its present preferredembodiment it will be obvious to those skilled in the art afterunderstanding my invention that various changes and modications may bemade therein without departing from the spirit or scope thereof.

What is claimed is:

A rotary mechanism comprising an outer body having spaced end walls anda peripheral Wall forming a cavity therebetween; an inner body disposedwithin said outer body for rotation relative to said outer body; saidinner body having a plurality of circumferentially-spaced 25 groovesabout its periphery; each of said grooves receiving a pair ofradially-movable, side-by-side seal strips for sealing cooperation withthe inner surface of said peripheral wall to form a plurality of Workingchambers between said bodies which vary in volume upon relative rotationof said bodies; the pair of apex seal strips in each groove extendingfrom one end face to the other of the inner body, and having a pluralityof spaced slits extending inwardly part Way from the radially outeredges of said strips and having an identical non-symmetrical spacing butwith said pair of strips being oppositely disposed in the groove so thateach strip covers said inwardly extending slits in the other of saidpair.

References Cited in the le of this patent UNITED STATES PATENTS1,617,863 Planche Feb. 15, 1927 2,027,594 Hutt Jan. 14, 1936 2,633,292Voznica Mar. 31, 1953 3,064,880 Wankel Nov. 20, 1962 FOREIGN PATENTS123,352 Great Britain Feb. 17, 1919 864,855 France May 7, 1941

